A conventional laser vapor deposition apparatus, such as the one shown in Japanese Unexamined Patent Publication No. SHO 59-116373, is shown in FIG. 1. In FIG. 1, a laser beam 1 changes its direction at a first plane mirror 2, and is condensed by a lens 3. The condensed laser beam 1 is introduced into a vacuum chamber 4 through a transparent window 5 formed in a wall of the chamber 4. The laser beam 1 which has entered into the vacuum chamber 4 through the window 5 changes its direction again at a second plane mirror 7 disposed within the chamber 4, so that the laser beam 1 impinges on the surface of a cylindrically shaped material 6 to be irradiated with the beam 1. The material 6 is disposed within the chamber 4 and rotates in a direction indicated by an arrow A. A heater 8 heats the whole material 6. A substrate 9 is disposed to face the material 6, and a shutter 10 is disposed between the material 6 and the substrate 9.
In operation, the laser beam 1 changes its direction at the first plane mirror 1 to pass through the lens 3 which condenses the laser beam 1, and enters into the vacuum chamber 4 through the transparent window 5. The second plane mirror 7 causes the beam 1 to change its direction again toward the surface of the material 6 which has been heated to a predetermined temperature by the heater 8. The focal length and the position of the condenser lens 3 are such that the focus point is located in the vicinity of a point on the material 6 to be irradiated with the laser beam 1. In the initial stage of the processing, when conditions are unstable, the surface of the substrate 9 is shielded by the shutter 10.
After various conditions have become stabilized, the shutter 10 is removed so that the substrate surface directly faces the material 6. The temperature at the surface of the material 6 irradiated with the laser beam 1 increases rapidly so that the material 6 is vaporized. The vapor of the material 6 is sputtered toward the substrate 9 and deposited on the substrate 9. The cylindrically shaped material 6 rotates in the direction A, and successive portions of the surface of the material 6 are heated and irradiated with the laser beam 1, and the material is vaporized and deposited to form a film on the substrate 9. In this process, part of the surface layer of the material 6 irradiated with the laser beam 1 is thermally decomposed. Those decomposition products which are more readily vaporizable are first vaporized from the surface of the material 6, and spread within the vacuum chamber 4 and exhausted out of the chamber 4. Then, even when the material 6 rotates so that the portion which has been irradiated moves out of the focus point of the laser beam 1, resulting in decrease of the temperature at that portion, and, accordingly, discontinuity of the thermal decomposition at the surface of the material 6, the composition of the surface layer of the material 6 to be irradiated with the laser beam 1 is no longer the same as the starting compound.
With the above-described conventional laser vapor deposition apparatus, the physical properties, such as the laser beam absorption coefficient and thermal conductivity, of the surface portion of the material 6 change more and more as they are irradiated more with the laser beam 1, so that the rate of evaporation of the material 6 cannot be maintained stable, and, furthermore, the composition of the deposit on the substrate cannot be maintained unchanged throughout the deposition process.
Therefore, an object of the present invention is to provide a laser vapor deposition apparatus which is free of the above-stated disadvantages, and in which a rate of evaporation of a material can be maintained stable and also the composition of the vapor deposited film can be maintained unchanged throughout the deposition.